The present invention relates to electrical connectors, and more particularly to high-density pin-grid-array (PGA) connectors.
The ongoing drive to reduce the size of electronic equipment, and to add additional functions to such equipment has resulted in a steady increase in the densities of electronic circuits. These increases in circuit densities and functionality have decreased the surface area available for mounting electrical connectors on printed wireboards and other types of circuit substrates. This development has generated a need for multi-pin electrical connectors having minimally-spaced terminal pins. High-density PGA connectors have been developed in response to this need.
Ball-grid array (BGA) connectors are a commonly-used type of PGA connector. FIG. 13 depicts a conventional BGA connector 100. FIG. 13, and the other figures included herein, are each referenced to a common coordinate system 11. The connector 100 comprises a connector body 102 and a plurality of terminal pins 104. The connector body 102 has a plurality of through holes 106 formed therein for receiving the terminal pins 104.
The connector 100 is formed using a plurality of solder balls 108. The solder balls 108 form solder joints that secure the connector 100 to a substrate such as a printed wireboard (PWB) (not shown). The solder joints also establish electrical contact between the terminal pins 104 and respective electrical connection points on the PWB. Each solder ball 108 is aligned with a terminal pin 104 and a respective electrical connection point, and then reflowed to establish a solder joint that electrically and mechanically couples the terminal pin 104 and the electrical connection point.
Aligning and reflowing the solder balls 108 represents additional process steps in the production of the connector 100. Applicants have found that these process steps, while sufficient for their intended use, have certain limitations and disadvantages. For example, the need to align and reflow the solder balls 108 adds to the cost and time needed to manufacture the connector 100. In addition, Applicants have found that aligning and reflowing the solder balls 108 becomes more difficult as the density of the terminal pins 104 is increased. In particular, these process steps are not easily programmable into an automated manufacturing system.
Applicants have found that the need to align and reflow the solder balls 108 precludes the use of a relatively efficient stress-assisted soldering process when forming the solder joints between the terminal pins 104 and the electrical connection points. The use of the solder balls 108 also makes it difficult to produce the electrical connector 100 without the use of lead, thus rendering the electrical connector 100 unsuitable for use in a lead-free environment. In addition, power and ground islands cannot readily be formed in the electrical connector 100 because of the difficulty in forming the solder balls 108 into solder joints that span two or more of the terminal pins 104.
Applicants have also determined that achieving effective mechanical and electrical coupling between the terminal pins 104 and the respective electrical connection points requires a relatively high degree of co-planarity among the terminal pins 104, the connector body 102, and the PWB. Such co-planarity is often difficult to achieve in a production environment due to factors such as normal part-to-part variations, limitations in the precision with which the components can be positioned and aligned, etc.
An ongoing need therefore exists for a high-density PGA connector that can be electrically and mechanically coupled to a circuit substrate without the use of solder balls.
A presently-preferred electrical connector comprises a plurality of electrically-conductive terminal pins and an electrically-insulative connector body. The connector body comprises a first and a second substantially planar surface and a plurality of stud members projecting from the second substantially planar surface. The connector body has a plurality of through holes formed therein. The through holes each extend from the first substantially planar surface to a respective stud member and are each adapted to receive a respective one of the terminal pins. At least a portion of each of the stud members is coated with an electrically conductive material.
Another presently-preferred electrical connector comprises an electrically-conductive terminal pin comprising a tab portion and a contact portion extending from the tab portion. The electrical connector also comprises an electrically-insulative connector body comprising a substantially planar main portion having a first through hole formed therein for receiving at least the tab portion, and a stud member projecting from a surface of the main portion and having an outer surface and an inner surface. The inner surface defines one of a recess and a second through hole that adjoins the first through hole and is adapted to at least partially receive the contact portion. At least a portion of the outer and the inner surfaces are coated with a substantially contiguous layer of an electrically conductive material.
Another presently-preferred electrical connector comprises an electrically-insulative connector body comprising a substantially planar main portion, and a stud member projecting from a surface of the main portion and being at least partially coated with an electrically-conductive material. The connector body has a passage formed therein. The passage extends through the main portion and the stud member. The electrical connector also comprises an electrically-conductive terminal pin at least partially disposed in the passage and contacting the electrically-conductive material.
Another presently-preferred electrical connector comprises an electrically-conductive terminal pin, and an electrically-insulative connector body comprising a first and a second substantially planar surface and a stud member. The stud member projects from the second substantially planar surface and is adapted to be mounted on a circuit substrate. The connector body has a through hole formed therein. The through hole extends from the first substantially planar surface to the stud member and is adapted to receive the terminal pin. At least a portion of the stud member is coated with an electrically conductive material adapted to establish electrical contact between the terminal pin and an electrical connection point on the circuit substrate.
A presently-preferred electrical component comprises a circuit substrate having an associated electrical circuit and an electrical connection point. The electrical component further comprises an electrically-conductive terminal pin, and an electrically-insulative connector body. The connector body comprises a first and a second substantially planar surface, and a stud member projecting from the second substantially planar surface and being mounted on the circuit substrate. The connector body has a through hole formed therein. The through hole extends from the first substantially planar surface to the stud member and is adapted to receive at least a portion of the terminal pin. The electrical component further comprises a layer of electrically conductive material disposed on at least a portion of the stud member to establish electrical contact between the terminal pin and the electrical connection point.